The present invention relates to a waterstop which is put in a construction joint of concrete and serves to prevent or bar passage or leakage of water through the joint.
In the prior art, it is known that passage or leakage of water through a construction joint of concrete can be prevented by use of a waterstop which is in a belt-like form of board provided on at least a part thereof with a layer of a water-swellable material. Such a conventional waterstop shaped in a continuous-length belt-like form is shipped from the manufacturer in a roll and transported to the site of construction where the rolled board is unrolled and cut in a length suitable for putting into the concrete joint. A problem frequently encountered in the construction works using such a waterstop is that the water-swellable layer thereof becomes inadvertently swollen with rain water or underground water prior to use in the course of transportation to and storage in the site of construction. Once the water-swellable layer has been prematurely swollen prior to use, the waterstop can be mounted on the concrete joint only with great difficulties or, in some adverse cases, the waterstop can no longer exhibit the proper preventing effect of water leakage through the joint.